Diaphragm



vNov. l1, 1930. H. c. HARRISON 1,781,387

DIAPHRAGM Filed July 5l, 1926 Patented Nov. 11, 1930 UNITED STATES PATENT OFFICE HENRY o. HARRISON, or PORT WASHINGTON, NEW YORK, AssIeNOR To EELI. TELE- PHONE LABORATORIES, INCORPORATED, OE NEW YORK, N.'Y., A CORPORATION or NEW YORK DIAIPHRAGM Application led July 31,

This invention relates to diaphragme and particularly to diaphragms of the piston or plunger type.

An object of the invention is to improve the operating characteristics of diaphragms, and particularly of diaphragms employed 4in acoustic devices, so as to obtain a more uniform frequency-response characteristic over a large portion of the sound frequency range.

A specific object is to increase the stiffness of the driven portion of a piston type diaphragm without appreciably increasing its mass.

As pointed out in my Patent 1,734,624, a

piston type diaphragm employed in an acoustic device, such as a phonograph reproducer or recorder, should preferably comprise a flexible peripheral portion and a stifened driven portion, both portions being of small mass. In the above noted patent there is described and claimed a plunger type diaphragm comprising a stiiened central portion and an annular flexible portion having corrugations tangential to the periphery of the stiffened portion. Y

1n accordance with the present invention improved. Operating characteristics are obtained by the use of al diaphragm having a plurality of stiiened areas -to which the driving or driven deviceJ is connected. In a preferred form of the invention, each stiffened area consists of a pyramidal elevation to the apex of which one arm of a driving spider is secured.

The invention may be better understood by referring to the accompanying drawing in which:

Fig. 1 is a sectional view of a phonograph reproducer or recorder employing the diaphragm of this invention Fig. 2 is a front elevation of the diaphragm of Fig. 1 showing the stiffening strips;

Figs. 3 and 4 are front and cross sectional views respectively of a modified form of diaphragm Without the stiifening strips. and the driving spider.

Fig. 5 is a front view of the diaphragm of Figs. 1 and 2 showing the driving spider attached without the stidening strips.'

Referring to the drawing, the diaphragm 1926. Serial N0. 126,313.

which consists of one piece of material is divided into three major portions, a stiifened or lcentral portion, a iiat marginal portion 21 and an intermediate iiein'ble portion 16. As shown, the central or stifened portion has embossed or otherwise formed therein a plurality of pyramidal elevations whose apices 15 are nearer the periphery than the center of said central port-ion. lThe opposing lateral faces 9 and 10 of adjacent elevations form dihedral angles and have common base lines or lateral edges 17. The center of the diaphragm is shown as slightly forward of the plane of the periphery. The baselines 17, therefore, define a conical surface having pyramidal elevations formed therein. i The lateral edges 8 are shown as concurrent lines in the same plane. Obviously, however, they may lie in different planes as they would be in the case Where the center of the diaphragm and the periphery are in the saine plane or the apices of the elevations and the center of the diaphragm in diierent planes. The iieXible portion 16 of the diaphragm is formed by corrugating a narrow band of the diaphragm near its circumference, said narrow band circumsciibing the pyramidal elevations. These corrugations extend approximatelytangentially to the outer edge of the sti'ened ortion substantially as shown in my Patent 1, 84,624 and although this structure is preferably einployed in conjunction with this invention, other constructions such as a plane or circularly corrugated marginal portion may 'be used. The diaphragm is mounted in a suitable housing or sound box 11 by securing the flat portion 21 between the clamping rings 22. Itis connected to the stylus arm 12 by the coupling member or spider 13. This spider comprises a stiii" dome-shaped central portion 13a and radially extending flexible arms 14.

These arms are clinched, spot welded or other` wise secured to the diaphragm at the apices 15 of the pyramidal elevations. The stylus bar 12 is secured to the dome-shaped central portion 13a at 27.

While an even number of pyramidal elevations may be employed, it is preferable, especially in diaphragms in which the center and the periphery of the stifi'ened portion are approximately in the same plane, to employ an odd number of the pyramids in order to avoid having the base lines 17 of diagonally opposite pyramids in a straight line and thus reduce the tendency of the diaphragm to iiex along this line due to applying unequal driving forces to the various stiened` areas. Additional stift'ening of the diaphragm is provided by the strips Whichmay be cemented or. otherwise secured tothe diaphragm along the angular groove formed by the sides of adjacent pyramids. These stiening strips may be made of any suitable'material, such as aluminum or one of its alloys.

ln Figs.v 3, l and 5 the stihening strips are not shown for the sake of clearness. ln Figs. 3 and which show a modiiied form of the diaphragm having an odd number of bosses, the driving spider is also omitted in. order to clearly illustrate the construction of the diaphragm.

ln accordance with this invention, not only is a diaphragm or portion thereof increased l in stiffness as a unit, Without increasing its Cil mass,'but the full advantages of a multiple point drive are realized by developing the stiened areas about the driving points so as to obtain the maximum stiness at these points. lt is desirable to have the central portion oi a piston type diaphragm Voi Sullicient stiness to be resonant at `frequencies above the range ordinarily employed in speech and music. lhen this ortion of the diaphragm is not uniformly stirt, thedriving force is preferably applied to the points of maximum stihness so that the piston portion of the diaphragm may move substantially as a unit rather-than in small resonant portions. Y T/Vliile thediaphragm shown described is of the piston type having a flexible peripheral portion and a stiffened driven portlon, the invention is not limited to this specic embodimentJ but includes other diaphragms employing a plurality oi stihfened areas, for example, a diaphragm employing the stiffened structure throughout supported at one or more oi the stiilened areas and driven at one or more oi the remaining stiiiened areas. rlhe diaphragm may also be oi relatively large dimensions so as to function eidciently in direct acting sound radiators. 'lhe term pyramidal as employed in describing the diaphragm tl invention is used to include conical and lations oi pyramidal and conical struct Mince the diaphragm l sound respon Vice it driven means may be c ph in. u

hat is claimed is:

2 p 1 i l. fr diapniagm nari p plurality of pyn. d pi We' Y A e? .-D' A rami ae tations renner- .iercin, an

3 means or holding the apices ci? said eleraarenas? having its apex at the center of the diaphragm.

3. A stiilened diaphragm having a plurality of pyramidal elevations having ad]oining bafses and stillening means securedto Said diaphragm at the junction of said elevations.

a. A stiilened diaphragm having a plurality of pyramidal elevations and reinforcing strips secured along the lower edges of said elevations.

5. A piston diaphragm comprising a stiened portion, having a plurality of pyramidal elevations embossed therein, and a exible portion having a plurality of substantially straight non-radial oorrugations.

6. piston diaphragm of thin material comprising a stiii'ened portion having a plurality of pyramidal elevations formed therein and a :Hexible portion `formed by corrugations arranged substantially tangentially to the periphery of the stiiened portion.

7. A piston diaphragm comprising a stili?- ened portion having a plurality of pyramidal elevations formed therein, a ilexihle portion integral with said stiilened portion, and means for holding the summits of said elevations in iixed spaced relation to each other.

8. ln an acoustic device, a piston dia'- phragm having a plurality of pyramidal elevations at its central portion and a dexihle annular portion integral therewith, and driving means connected to each of said pyramidal elevations.

9. ln an acoustic device, a diaphragm having a portion stiiened by a plurality of pyramidal elevations, and a driving means connected to the apices of a plurality of said pyramidal elevations.

l0. A sound recorder and reproducer comprising a stylus bar, a diaphragm having a plurality of sti'ened areas, a spider having a still central portion and flexible radial arms connecting said stylus bar and said diaphragm', the stylus bar being connected to the central portion of said spider and the stiliened areas of the diaphragm being connected to the radial arms of said spider.

il. ln an acoustic device, a diaphragm comprising a central piston portion oi substantial area and a flexible annular portion. said central portion being divided eaually into a small number oi pyramidai sectors haring their apices nearer 'tee than the center of said central portion.

i2. A diaphragm comprising e central portion and a ilenible annular portion, said eral edges meeting at the center of the phragn.

weier 13. A diaphragm of thin material having a central portion comprisinga small number of formed-up pyramidal elevations having adjacent base angles at the center of said central portion and apices at a substantial distance therefrom.

111. In an acoustic device a diaphragm of thin material comprising a central portion having a plurality of similar pyramidal elevations formed therein, said elevations having base angles adjacent the center and apices at a substantial distance therefrom, and means connected with eac-h of said apices `tor driving said diaphragm.

15. A diaphragm comprising a disc of thin sheet material having a plurality of formedup pyramidal elevations, the opposing lateral faces of adjacent elevations forming equal dihedral angles.

16. In an acoustic device, a diaphragm comprising a plurality of adjacent elevations in the form of pyramids, the apices of said pyramids lying between the center and the periphery, and means connected to the apices of saidv elevations for driving said diaphragm.

17. Al diaphragm having a plurality of py ramidal elevations formed therein, said elevations having concurrent lateral edges lying 3o in the same plane.

In Witness whereof, I hereunto subscribe my name this 27th dayof July, A, D. 1926.

HENRY C. HARRISON. 

